RESPONSE OF RADIAL GROWTH OF PINUS DENSATA FOREST TO CLIMATE CHANGE IN MILIN CITY OF XIZANG,CHINA
Pinus densata coniferous forest is widely distributed in Milin City of southeast Xizang of China and is little disturbed by human activities,showing the high dendrochronological potential.Herein,Pinus densata forest in Milin City of southeast Xizang(29°14′N,94°13′E,2950 m a.s.l.)is selected as the research object.We aim to establish the standard tree-ring-width chronology and explore its responses to climate change.Based on the ring-width data from 53 tree individuals,we constructed a highly replicated tree-ring width chronology with a length of 313 years(1709～2021).The representative interval for this chronology changes from 1935 to 2021(EPS＞0.85),the correlation between cores is 0.353,and the mean sensitivity is 0.32.Five climatic variables(monthly average temperature,monthly maximum temperature,monthly minimum temperature,monthly precipitation,and monthly Palmer Drought Severity Index(PDSI))between 1901 and 2021 used in this study were extracted from the CRU TS 4.1 dataset(spatial resolution:0.5°x0.5°).Results of correlation analysis and partial correlation analysis showed that the radial growth of Pinus densata was significantly positively correlated with average minimum temperature in November of the previous year and average minimum temperature and average temperature in current August,but it was significantly negatively correlated with the precipitation in current June.Among different climatic variables,the highest correlation was found between tree growth and precipitation of current April,suggesting that a lack of precipitation in the early growing season limited its radial growth.Changes in the number of missing rings in Pinus densata over the last century showed a significant upward trend,and it was significantly positively correlated with the monthly PDSI from previous September to current April,indicating that drought stress at the beginning and end of the growing season was unfavorable for tree growth.Moving correlation analysis further revealed that April precipitation played a dominant role in controlling radial growth of trees.The climate of Milin city had become warmer and drier in the past century,and it is characterized by uneven distribution of seasonal precipitation,thereby leading to the water limitation for radial growth of trees.Ongoing climate warming in the future may threaten the growth and health of the Pinus densata forest in Milin City.The above conclusions can provide a reference for the management and protection of coniferous forest in Xizang under rapid climate change.
tree-ringclimate changewarm and dry climatePinus densatamissing ring
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